This book started out as a "Manual. " The idea was to offer straightforward instruction on how to handle patients in whom renal function is altered by intrinsic as well as systemic or extrarenal disease. While we have attempted to provide simple approaches to most conditions, we have gone beyond that and offer here more detailed description of pathophysiology, diagnosis and therapy. Thus, the "Manual" has become a Handbook. In so doing we hope we have widened the audience for which the book may be useful. As it now stands, we envision that students, house staff, nephrology trainees, nephrologists, primary-care physicians, and nurses of specialized units, interested in kidney-related disturbances and in alterations of the composi­ tion of the extracellular fluid, will benefit from reading the Handbook. While providing a rational background for the treatments outlined, each author has attempted to narrate the reasons why such therapy is utilized. Frequently, the information is provided in tables and figures to which ready reference can be made. The flow-chart approach has also been utilized to illustrate pathophysiological sequence or steps in therapy. In most instances, the discussion of pathophysiology has been limited to what is widely ac­ cepted rather than treading into anything controversial, unless the nature of the problem or the nature of our knowledge is ambiguous.